Experienced, but not naïve, birds use herbivore-induced plant volatiles to locate prey, learning one tree species at a time.

In tritrophic interactions, birds are able to detect herbivore-induced plant volatiles and use them as a signal of presence of arthropods on plant. It remains unclear whether this ability is innate or learned and how the birds react to novel odours. We studied whether and how naïve and trained great tits (Parus major) discriminate between herbivore-induced and noninduced saplings of potentially familiar and novel plant species. Birds trained to discriminate between saplings of either novel or familiar plant species preferred the induced saplings of the plants species they were trained to. Naïve birds did not show any preferences. Our results indicate that the attraction of great tits to herbivore-induced trees is not innate. Yet, the skill can be acquired through learning and novelty of the odour doesn’t seem to be important. This implies that birds are learning whole bouquets of the herbivore-induced volatile compounds, rather than specific compounds individually.